Yuna is a spirited and energetic human fourth-grade girl living on the fictional Izayoi Island, Japan's southernmost tip, with a proficiency in karate. Her life changes when Stitch crash-lands on the island after escaping a space storm. Yuna informs Stitch about the mystical Stone of Chitama, explaining its power to grant wishes requires performing 43 good deeds, establishing their shared objective and partnership.

Previously an ordinary island resident, Yuna later relocates from Izayoi Island to an urban setting called "New Town" in Okinawa. This move forces her to adapt to unfamiliar surroundings, attend a new school, and form relationships with different peers. Throughout these changes, she clings to her determination and optimism.

Yuna's narrative centers on her deepening bond with Stitch, evolving them from collaborators to inseparable companions. This relationship fuels mutual growth, with Yuna guiding and grounding Stitch as he learns human social norms and pursues good deeds. Her story consistently explores friendship, adaptability, and perseverance across varying circumstances.